As a conventional system for manually operating mechanical equipment, a system in which a manual operation panel is fixedly installed for each area where an operator can visually recognize a control target or a system which utilizes, as described in Japanese Published Unexamined Patent Application: No. 2015-214378 (Patent Literature 1), an operation terminal carried by an operator entering the site of the mechanical equipment, that is, an operation terminal which is brought into a connected state by a communication means to a control device of the mechanical equipment in front of the operator has been known. In the former system of hardware configuration in which the fixedly installed manual operation panel is used, as the scale of the mechanical equipment is increased, the number of manual operation panels installed is increased, and moreover, the number of operation switches included in each of the manual operation panels is significantly increased, with the result that the cost of the equipment including wiring between the control target and the control device is significantly increased. By contrast, with the latter system of software configuration which utilizes the portable operation terminal, it is possible to significantly decrease the cost of the equipment.